This invention relates to means for simultaneously dispensing two liquids which are held in separate spaces within a container, preferably in a manner that allows the relative proportions of the liquids dispensed to be varied.
Such dispensing means are known in which one liquid is held in a main outer container within which there is a secondary inner container, holding the other of the two liquids. The fluid-holding spaces of both containers can communicate with a common outlet and both containers are pressure-deformable, so that squeezing the outer container pressurizes the contents of both to discharge the two liquids together through the common outlet.
These known dispensing means include that shown in GB 1241985 in which a dispensing unit is mounted in the neck of an outer container holding a base solution, the unit itself comprising an annular secondary container fitting within the main container to seal with the inside wall of the container neck. The annular container forms a central passage open at its inner end to the main volume of the outer container and at its upper end to an outlet nozzle in the centre of a cap screwed onto the neck of the main container. A pair of concentric cylindrical sleeves formed integrally with the secondary container project from that container towards the screw cap outlet nozzle. The sleeves define an annular space into which the liquid in the secondary container can flow through apertures in the bottom wall between the pair of concentric sleeves. An internal cylindrical collar on the cap protrudes into the annular space formed by the sleeves and forms a sliding seal with the inner face of the outer of those sleeves. The collar has a chamfered end opposed to the end of the inner sleeve and forms therewith a restriction in the path of flow from the annular space to a mixing chamber preceding the outlet nozzle.
When the main container is inverted and squeezed, the base solution flows through the central passage surrounded by the secondary container to the mixing chamber. At the same time the hydrostatic pressure in the main container forces liquid from the secondary container through the annular space to mix with the main fluid in the mixing chamber before the combined liquids issue from the outlet nozzle. The mixing is promoted by the widening of the flow passages following the restriction in the path of the secondary container fluid and complete mixing is further ensured by vanes in the flow passage immediately preceding the outlet nozzle. By screwing the cap in to a greater or lesser extent, the restriction is made more or less pronounced and the proportion of secondary liquid to main liquid is correspondingly reduced or increased.
In U.S. Pat. Nos. 3,217,931 and 3,289,887 further two-fluid dispensing means are described. These include devices in which, before they are discharged, the flows of two liquids become thoroughly mixed in a mixing space formed between an outlet nozzle of the device and a series of internal orifices through which the individual fluids are discharged from respective containers. Further devices described in U.S. 3,217,931 discharge the fluids in separate streams with no intermixing until after they have left the container. The various forms of device described in these two specifications do not have the ability to vary the proportions of the fluids being dispensed. A similar fixed ratio dispensing device which also ejects streams of the two liquids side by side is described in GB 965508.
Further examples of means for dispensing two fluids together are shown in U.S. Pat. No. 3,876,111 which has a number of small metering slots for the main fluid while the secondary fluid flow takes place past a central plug mounted in a screw cap of the device. By unscrewing the cap the plug is displaced to leave a narrow annular flow channel to an exit chamber into which the metering slots also open. Mixing of the flows is thus promoted before they are discharged. It is described how, by adjusting the screw cap, it is possible to open more or fewer slots to vary the proportions of the two fluids. In each case the fluids are metered through relatively narrow passages into a larger space or plenum before they are discharged through an outlet nozzle so that turbulent mixing is promoted.
Other examples of dispensing means in which two liquids are mixed before ejection can be found in GB 1107873.
The prior mixing of the two liquids before discharge in these known multi-fluid dispensing means has practical advantages for many typical liquids dispensed. The minor constituent is typically a concentrate or additive and direct contact with it before dilution may be undesirable. In the prior art in which the two liquids escape side by side, whether as a single jet or in separate jets, it may be necessary to exercise considerable care to avoid concentrate falling where it may be harmful or unpleasant. Particularly where the dispensers are used for consumer products, safety and consumer acceptability may thus make it necessary to ensure thorough mixing of the two fluids before discharge.
If these known devices mix two liquids having a different appearance, the hue of the mingled flow is an indication of their relative proportions, which could be particularly useful if the dispensing device permits the proportions to be varied. For consumer products, however, which must allow for the unskilled use of the dispensers by a wide variety of individuals, some possibly with imperfect vision, it is difficult to ensure that the appearance of two mixed liquids can indicate sufficiently clearly their relative proportions. It is particularly difficult if one of the fluids forms only a very small part, e.g. 1-2%, of the mixture.